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DOWN SYNDROME


 DEFINITION 

two days ago Mbah Dukun Bagong visit his hometown, he met his old friend, he saw his friend's daughter. her face look freaky, like mongoloid face, whats wrong with her?

Down Syndrome, Trisomy 21 or Mongolism, was first described by Dr. Langdon Down in 1865. At that time, the diagnosis of the syndrome was based solely on physical findings. Down syndrome isn't a disease. Down Syndrome is a genetic condition. As the word syndrome implies, it is a collection of common characteristics that is evident not only physically, but also by a degree of learning disability.



ETIOLOGY
Down syndrome is usually caused by an error in cell division called "nondisjunction."  Nondisjunction results in an embryo with 3 copies of chromosome 21 instead of the usual two.  Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate.  As the embryo develops, the extra chromosome is replicated in every cell of the body.  This type of Down syndrome, which accounts for 95% of cases, is called Trisomy 21.
Chromosomes are in simple terms the ‘building blocks’ that give us our individual characteristics, for example, blue eyes, blonde hair etc. Similarly, people with Down Syndrome, who share this extra chromosome, also share common physical features.
Note, the number and structure of chromosomes within an individual cell is referred to as the karyotype of a cell. The term mongolism, mongoloid or mongoloid idiot are outdated and stigmatizing terms and should not be used to describe persons with this condition. The etiology of Down Syndrome relates to the problem of nondisjunction of a 21 chromosome during oogenesis, thus an extra 21 chromosome is provided to the offspring by the mother. Recent studies also implicate paternal etiology through nondisjunction during spermatogenesis.



TYPES of DOWN SYNDROME
There are 3 types of Down Syndrome, although it is generally thought that there is no clinical difference in the three genotypes.
(1) Trisomy 21 (94%): The extra 21 chromosome (three instead of the usual two) produces a complement of 47 chromosomes. Trisomy 21 may also be referred to as Trisomy G.
(2) Translocation (5%): A segment of a 21 chromosome is found attached to other pairs of  chromosomes (usually #14, thus referred to as a 14/21 translocation). These individuals have the normal complement of 46 chromosomes.
(3) Mosaicism (1%): Nondisjunction occurs at a later stage of cell division, therefore, some cells have the normal complement of 46 chromosomes and other cells 47 chromosomes (with an extra 21 chromosome).

The two other types of Down syndrome are called mosaicism and translocation.  Mosaicism occurs when nondisjunction of chromosome 21 takes place in one-but not all-of the initial cell divisions after fertilization.  When this occurs, there is a mixture of two types of cells, some containing the usual 46 chromosomes and others containing 47.  Those cells with 47 chromosomes contain an extra chromosome 21.  Mosaicism accounts for about 1% of all cases of Down syndrome.  Research has indicated that individuals with mosaic Down syndrome may have fewer characteristics of Down syndrome than those with other types of Down syndrome.  However, broad generalizations are not possible due to the wide range of abilities people with Down syndrome possess.
 Translocation accounts for about 4% of all cases of Down syndrome.  In translocation, part of chromosome 21 breaks off during cell division and attaches to another chromosome, typically chromosome 14.  While the total number of chromosomes in the cells remain 46, the presence of an extra part of chromosome 21 causes the characteristics of Down syndrome.
Regardless of the type of Down syndrome a person may have, all people with Down syndrome have an extra, critical portion of chromosome 21 present in all or some of their cells.  This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome. 
The cause of nondisjunction is currently unknown, but research has shown that it increases in frequency as a woman ages.  However, due to higher birth rates in younger women, 80% of children with Down syndrome are born to women under 35 years of age.  There is no definitive scientific research that indicates that Down syndrome is caused by environmental factors or the parents' activities before or during pregnancy.
 Once a woman has given birth to a baby with Trisomy 21, it is estimated that her chances of having another baby with Trisomy 21 is 1% greater than her chances by age alone.
The age of the mother does not seem to be linked to the risk of translocation.  Most cases are sporadic-that is, chance events.  However, in about one third of cases, one parent is a carrier of a translocated chromosome.  The risk of recurrence of translocation is about 3% if the father is the carrier and 10-15% if the mother is the carrier.  Genetic counseling can determine the origin of translocation. 



SYMPTOMS and SIGNS 
What are the characteristic features and symptoms of Down syndrome?
Although the severity of Down syndrome ranges from mild to severe, most individuals with Down syndrome have widely recognizable physical characteristics. These include:
•    a flattened face and nose, a short neck, a small mouth sometimes with a large, protruding tongue, small ears, upward slanting eyes that may have small skin folds at the inner corner (epicanthal fold);
•    white spots (also known as Brushfield spots) may be present on the colored part of the eye (iris);
•    the hands are short and broad with short fingers, and with a single crease in the palm;
•    poor muscle tone and loose ligaments are also common; and
•    development and growth is usually delayed and often average height and developmental milestones are not reached.
DIAGNOSIS
How is Down syndrome Diagnosed?
A. Prenatally
There are two types of tests for Down syndrome that can be performed before a baby is born: screening tests and diagnostic tests. Prenatal screens estimate the chance of the fetus having Down syndrome. These tests only provide a probability. Diagnostic tests can provide a definitive diagnosis with almost 100% accuracy.
 Most screening tests involve a blood test and an ultrasound (sonogram). The blood tests (or serum screening tests) measure quantities of various substances in the blood of the mother. Together with a woman's age, these are used to estimate her chance of having a child with Down syndrome. These blood tests are often performed in conjunction with a detailed sonogram to check for "markers" (characteristics that some researchers feel may have a significant association with Down syndrome). Recently, researchers have developed a maternal serum/ultrasound/age combination that can yield a much higher accuracy rate at an earlier stage in the pregnancy. Still, the screen will not definitively diagnose Down syndrome.
 Prenatal screening tests are now routinely offered to women of all ages. If the chance of having a child with Down syndrome is high from prenatal screening, doctors will often advise a mother to undergo diagnostic testing if they desire a definitive diagnosis.
The diagnostic procedures available for prenatal diagnosis of Down syndrome are chorionic villus sampling (CVS) and amniocentesis. These procedures, which carry up to a 1% risk of causing a spontaneous termination (miscarriage), are practically 100% accurate in diagnosing Down syndrome. Amniocentesis is usually performed in the second trimester after 15 weeks of gestation, CVS in the first trimester between 9 and 11 weeks. 
B. At Birth
Down syndrome is usually identified at birth by the presence of certain physical traits: low muscle tone, a single deep crease across the palm of the hand, a slightly flattened facial profile and an upward slant to the eyes.  Because these features may be present in babies without Down syndrome, a chromosomal analysis called a karyotype is done to confirm the diagnosis. To obtain a karyotype, doctors draw a blood sample to examine the baby's cells. They use special tools to photograph the chromosomes and then group them by size, number, and shape. By examining the karyotype, doctors can diagnose Down syndrome.  Another genetic test called FISH can apply similar principles and confirm a diagnosis in a shorter amount of time.


MANAGEMENT
Can a baby with Down syndrome be cured?
There is no cure for a child born with this condition but many symptoms can be treated and special early intervention programs are enabling these individuals to develop to their potential.
A child with Down syndrome can usually do most things that any young child can do such as walking, talking, dressing and being toilet trained although they may do these things later than other children.
How is Down syndrome managed?
Although the genetic cause of Down syndrome is known, there is currently no cure. Due to advances in technology, scientists are slowly beginning to understand which genes when present in three copies are responsible for which Down syndrome characteristics, but it will take many years to fully grasp the complex interplay between the different genes. Much research to date is focused on understanding the causes of impaired cognition in Down syndrome and on finding potential therapies that might improve learning. Most of these studies are carried out using animal models of Down syndrome, but some human clinical trials involving potential therapies are also being conducted.
Corrective surgery for heart defects, gastrointestinal irregularities, and other health issues is necessary for some individuals. Regular health checkups should be scheduled to screen for other conditions such as visual impairments, ear infections, hearing loss, hypothyroidism, obesity, and other medical conditions. Individuals with Down syndrome should be fully included in family and community life

Who is at risk of having a child with Down syndrome?
In an individual with Down syndrome, the extra copy of chromosome 21 can come from either the egg or the sperm. It has been shown, however, that as a woman gets older, her chance of having a child with Down syndrome increases, as shown in. In particular, a woman who is 35 years or older at the time of delivery of her baby, has an increased chance of having a baby with Down syndrome.

3 comments:

  1. wow... can't tahan looking at that alll...
    hope everybody will be fine

    ReplyDelete

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